The present invention relates to a drum with a head adjusting device.
Drums such as bass drums and snare drums include head adjusting devices located around its body for adjusting the tension of a drumhead (for example, Japanese Laid-Open Patent Publication No. 05-307383). FIG. 6(a) is a cross-sectional view illustrating one example of such a head adjusting device. FIG. 6(a) shows a head adjusting device for adjusting the tension of the upper head.
As shown in FIG. 6(a), a drum 22 includes a cylindrical body 2 having upper and lower openings. A disk-like upper head 3 and a lower head (not shown) are provided at the upper and lower ends of the body 2 to close the openings. An annular upper head frame 5, which can be fitted to the outer circumference of the body 2, retains the outer circumferential rim of the upper head 3. An upper hoop 6 covers the outer circumference and the top of the upper head frame 5. The lower surface of the upper hoop 6 abuts against the upper surface of the upper head frame 5. The upper hoop 6 is separate from the body 2.
A head adjusting device 23 for adjusting the tension of the upper head 3 includes a lug 7, which is secured to the periphery of the body 2, a lug nut 8, which is located at the upper end of the lug 7, and a lug bolt 9, which couples the lug nut 8 to the upper hoop 6. The lug bolt 9 is inserted through the upper hoop 6 from above the drum 22 and is threaded into the lug nut 8 at its distal end. When adjusting the tension of the upper head 3, the lug bolt 9 is selectively tightened or loosened with respect to the lug nut 8 so that the upper head frame 5 is shifted along the axial direction via the upper hoop 6.
When playing the drum 22, the lug bolt 9 might be loosened by strong vibration of the upper head 3, and the drum 22 might go out of tune. Therefore, several structures have been proposed to prevent undesirable loosening of the lug bolt 9. For example, a head adjusting device 23 has been proposed that has a thin rubber sheet 11 below the lug nut 8. An oval hole 12 is formed in the rubber sheet 11 to permit the distal end of the lug bolt 9 to be inserted therethrough (see FIG. 6(b)). The lug bolt 9 is prevented from being undesirably loosened by press-fitting the rubber sheet 11 to the root of a threaded portion 9b formed on the periphery of the distal end of the lug bolt 9.
However, since the rubber sheet 11 has high elasticity and flexibility, although the rubber sheet 11 is press-fitted to the root of the threaded portion 9b of the lug bolt 9, the vibration of the upper head 3 might not be suppressed sufficiently. Furthermore, when continuously playing the drum 22 for a long period, there is a high possibility that the lug bolt 9 will be gradually loosened regardless of the player's intention.
Another structure (not shown) for preventing loosening of the lug bolt 9 has been proposed that uses an annular member made of nylon instead of the rubber sheet 11. A bore, which has a slightly smaller diameter than the outer diameter of the lug bolt 9, is formed in the annular member. Since the lug bolt 9 is threaded into the bore, great frictional force is generated between the annular member and the threaded portion 9b of the lug bolt 9. As a result, the lug bolt 9 is prevented from undesirably rotating by shocks and vibration. On this point, the structure prevents the lug bolt 9 from being loosened even if the drum 22 is played for a long time, more reliably than the case where the rubber sheet 11 is provided. However, in this case, the torque required for tightening the lug bolt 9 is increased and a special tuning key must be used. As a result, the tuning process becomes troublesome. Also, the annular member will deform after a long period of usage and the frictional force will be reduced. This might gradually cause undesirable loosening between the annular member and the lug bolt 9.
As other structure for preventing undesirable loosening, a structure in which another lock nut is provided on the lug bolt 9 above the lug nut 8 to doubly couple the lug nut 8 and a structure in which a thin plate-like member made of plastic is provided between the head of the lug bolt 9 and the upper hoop 6 to prevent unintentional rotation have been proposed. However, in these cases, the lock nut must be loosened or the thin plate-like member must be removed every time the drum 22 is tuned. Therefore, the tuning process is complicated.